The invention relates to a valve arrangement in general.
This valve arrangement is adapted to adjust the idling speed of internal combustion engines having an intake manifold and a throttle valve in the manifold by controlling the quantity of air on the intake side of the intake manifold leading to the internal combustion engine. The arrangement includes a bypass of the throttle valve and an electromechanical setting element including a solenoid arranged to move a closure member for the bypass via a setting member in an opening direction against the force of a return spring. The closure member is also biased in the opening direction by the pressure on the admission side of the manifold. The admission side is connected via channels to a chamber which has a movable wall which is connected to a rear portion of the closure member.
Such a valve arrangement serves to keep the idling speed of the engine as low as possible while at the same time regulating the speed of the engine in such a manner that when additional loads are applied, such as, loads caused by auxiliary units, the idling speed is not reduced to such an extent that the engine stalls. To accomplish this result the solenoid is acted on by a setting current which is generated, inter alia, as a function of the actual speed of the engine. This current causes a displacement of the closure member such that the actual speed of the engine reaches a predetermined desired speed substantially independent of any disturbing variables.
When the solenoid is not acted on by current, the setting member and, together with it, the closure member are typically moved by the return spring either into a completely open position or into a completely closed position. This occurs when no current acts on the solenoid because the vehicle is not moving. A lack of current may also be caused, however, by a defect in the circuit which supplies current to the solenoid.
In the traditional valve arrangements of this type a lack of current to the solenoid thus results in the engine either operating at maximum idling speed or operating at minimum idling speed, with danger of stalling.
It is an object of the invention, therefore, to create a valve arrangement of this type which, while being of simple construction, assures, upon failure of the solenoid, the lowest possible idling speed consistent with prevention of stalling of the engine.